The arguments are the name of the stack and the id of the revision to reset to. If the stack is not specified, then it defaults to whichever stack is currently marked as the default. The stack can also be specified using the --stack option. Some examples:

Peform reset on the stack with the given NAME. Defaults to the name of whichever stack is currently marked as the default stack. Use the stacks command to see the stacks in the repository. This option is silently ignored if the stack is specified as a command argument instead.